Simultaneous CO2 capture and functionalization: solvated electron precursors as novel catalysts

Metal complexes with diffuse solvated electrons are proposed as alternative catalysts for the simultaneous CO2 capture and utilization. Quantum chemical calculations were used to study the reaction of CO2 with...

Shallow and deep trap states of solvated electrons in methanol and their formation, electronic excitation, and relaxation dynamics

We present condensed-phase first-principles molecular dynamics simulations to elucidate the presence of different electron trapping sites in liquid methanol and their roles in the formation, electronic transitions, and relaxation of solvated electrons (e−met) in methanol. Excess electrons injected into liquid methanol are most likely trapped by methyl groups, but rapidly diffuse to more stable trapping sites with dangling OH bonds. After localization at the sites with one free OH bond (1OH trapping sites), reorientation of other methanol molecules increases the OH coordination number and the trap depth, and ultimately four OH bonds become coordinated with the excess electrons under thermal conditions. The simulation identified four distinct trapping states with different OH coordination numbers. The simulation results also revealed that electronic transitions of e−met are primarily due to charge transfer between electron trapping sites (cavities) formed by OH and methyl groups and that these transitions differ from hydrogenic electronic transitions involving aqueous solvated electrons (e−aq). Such charge transfer also explains the alkyl-chain-length dependence of the photoabsorption peak wavelength and the excited-state lifetime of solvated electrons in primary alcohols.

The Ag+ Reduction Process in a Plasma Electrochemical System Tuned by the pH Value

The interactions between discharge plasmas and an aqueous solutions can enable the production of reactive species and charge transfer at the plasma-liquid interface, forming the plasma electrochemical system (PES). The PES are promising for diverse applications, such as nanomaterials synthesis, due to the activation of the solution chemistry by the plasma. In this paper, we investigate the influence of the solution’s pH value on the formation of silver nanoparticles (AgNPs) in a direct current (DC) PES. Dual argon DC plasmas are generated in an H-type electrochemical cell containing an aqueous solution of silver nitrate with pH values in the range of 1.99-10.71. By this design, the solution acts as a cathode at one end of the H-type cell, and as an anode at the other end. The results show that the AgNPs are formed at the anode except for the solution with the pH value of 1.99. However, at the cathode, the AgNPs only appear in the solution with the pH value of 10.71. We find that the solvated electrons and hydrogen peroxide produced by the plasma-liquid interactions are responsible for the Ag+ reduction at the solution anode and the solution cathode, respectively.

Early dynamics of the emission of solvated electrons from nanodiamonds in water

Solvated electrons are among the most reductive species in aqueous environment. Diamond materials have been proposed as a promising source for solvated electrons, but the underlying emission process in water remains elusive so far. Here, we show spectroscopic evidence for the emission of solvated electrons from nanodiamonds upon excitation with both deep ultraviolet (255 nm) and visible (400 nm) light using ultrafast transient absorption. The crucial role of surface termination for the emission process is evidenced by comparing hydrogenated, hydroxylated and carboxylated nanodiamonds. Especially, hydrogenated nanodiamonds are able to generate solvated electron upon visible light excitation, while they show a sub-ps recombination due to trap states when excited with deep ultraviolet light. The essential role of surface reconstructions on the nanodiamonds in these processes is proposed based on density functional theory calculations. These results open new perspectives for solar-driven emission of solvated electrons in aqueous phase using nanodiamonds.

Effect of voltage polarity and supply frequency on properties of plasma contacting liquid electrode and gold nanoparticle synthesis

Plasma contacting with liquid provides many charged particles and reactive species into the liquid. The difficulty in controlling or selecting each specific species has significantly limited its applications in industry. Here, we present a study on using voltage polarity to regulate the type of charged particles absorbing from plasma into liquid. Detailed understanding of the processes at the plasma-liquid interface, electrolysis due to switching in voltage polarity was investigated via a visual pH observation, measuring the concentration of H2O2 and solvated electrons. The results indicated that changing in voltage polarity strongly affects the plasma properties, chemical properties, and electrolysis process in liquid, and further in the types of reducing species for gold nanoparticle synthesis. The results also showed using a suitable frequency could improve the efficiency of absorption of H2O2from plasma into the bulk liquid and the yield in the production of gold nanoparticles. The results provide a way to select desired species from plasma into the liquid for a distinct purpose and accompanying other properties in the system of plasma contacting with liquid.